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Crop Growth and Development
1. Vegetative and reproductive development, and senescence
2. Photosynthesis, respiration and assimilation
3. Plant growth regulators
Life Cycles of Flowering Plants
Seed
Embryo Phase
Juvenile Zygote
Annual, Biennial
Seed
Embryo Phase
Juvenile Phase
Zygote
Flower
Juvenile Phase
Adult Phase
Zygote
Senescence
Flower Adult Phase
Axillary buds
Perennial
Reproductive Growth Vegetative Growth
Senescence
Vegetative DevelopmentVegetative Development
What is Vegetative Development?
Vegetative development is thegeneration of leaves, stems androots on a plant.
Phases of Vegetative Development
� Emergence and elongation of roots
� Emergence and development of shoot (leaves, stem, axillary buds)(leaves, stem, axillary buds)
Vegetative Structures
� Leaves
- simple leaf
- compound leaf
� Stems
- contain buds, nodes
- modified stems: tuber (eg. potatoes), rhizome (eg. ginger), bulb (eg. onion),
Simple leaf Compound leaves
pinnate palmate
corm (eg. water chestnut), stolon (eg. grasses, strawberry)
� Roots
- tap root (eg. rubber tree)
- fibrous root (eg. rice, maize, palms, grasses)
- aerial root (eg. orchid)
- adventitious root
- modified roots: tuberous root (eg. sweet potatoes)
De Hertogh and Le Nard (1993) The Physiology of Flower Bulbs. Elsevier Scientific Publisher. Amsterdam,
The Netherlands.
Leaf Anatomy
cuticle
upper epidermis
lower epidermis
spongy mesophyll
cuticle
palisade mesophyll
bundle sheath cellxylem
phloem
stomata guard cell
vascu
lar
bu
nd
le
Vegetative Structures
� Leaves
- simple leaf
- compound leaf
� Stems
- contain buds, nodes
- modified stems: tuber (eg. potatoes), rhizome (eg. ginger), bulb (eg. onion),
Simple leaf Compound leaves
pinnate palmate
corm (eg. water chestnut), stolon (eg. grasses, strawberry)
� Roots
- tap root (eg. rubber tree)
- fibrous root (eg. rice, maize, palms, grasses)
- aerial root (eg. orchid)
- adventitious root
- modified roots: tuberous root (eg. sweet potatoes)
De Hertogh and Le Nard (1993) The Physiology of Flower Bulbs. Elsevier Scientific Publisher. Amsterdam,
The Netherlands.
Vegetative Structures
� Leaves
- simple leaf
- compound leaf
� Stems
- contain buds, nodes
- modified stems: tuber (eg. potatoes), rhizome (eg. ginger), bulb (eg. onion),
Simple leaf Compound leaves
pinnate palmate
corm (eg. water chestnut), stolon (eg. grasses, strawberry)
� Roots
- tap root (eg. rubber tree)
- fibrous root (eg. rice, maize, palms, grasses)
- aerial root (eg. orchid)
- adventitious root
- modified roots: tuberous root (eg. sweet potatoes)
De Hertogh and Le Nard (1993) The Physiology of Flower Bulbs. Elsevier Scientific Publisher. Amsterdam,
The Netherlands.
Reproductive DevelopmentReproductive Development
What is Reproductive Development?
Reproductive development refers to the initiation and development of flowers, fruit and seeds on a plantplant
Phases of Reproductive Development in Flowering Plants
� Flower induction and initiation
� Flower differentiation and development
� Pollination
Fertilization� Fertilization
� Fruit set and seed formation
� Growth and maturation of fruit and seed
� Fruit senescence
Flower Structure
stigma
style
anther
filament
stamen
style
petal
ovule
ovary
sepal
receptacle
pistil
Flower Induction and Initiation
� Photoperiod (daylength)
� Low temperature induction
� Self-induction
Photoperiod
Behaviour of Short-day Plants
Behaviour of Long-day Plants
Light regime
� Long-day plants: only flower under a long daylength (e.g. oat, wheat)
� Short-day plants: only flower under a short daylength or require a certain period of darkness which is uninterrupted by light for flower induction (e.g. soybean, poinsettia, Chrysanthemum morifolium)
� Day-neutral plants: flower induction is not affected by daylength (e.g. grapes, corn, tomato)
24 hours
Light interruption
Critical night length
Vegetative
Flowering
Vegetative
Flowering
Vegetative
Flowering
Low Temperature Induction
� Vernalization is a cold temperature treatment that induces flowering
� Temperature and length of vernalization period vary among species or even cultivars of the same species
� Range of temperatures: 0oC – 10oC
� Examples:
� brussel sprouts
� carrots
� celery
� barley
� oats
� wheat
Self-Induction of Flowering
� Many plants are self-inductive for flowering
� Initiate or form flowers at almost any photoperiod andwithout vernalization
� Start to flower when they reach a certain developmentalstage or maturity
� Examples:
� Garden perennials: roses, carnations, gerbera
� Garden annuals
� Vegetables crops: cucumber, beans, peas, tomatoes
Pollination
� Pollination is the release, transfer and deposition of pollen from an anther to a stigma
� Agents of pollination:
� Animals (insects, birds, snails, bats)
>90% of flowering plants� >90% of flowering plants
� Wind
� Water
Fertilization
� Double fertilization:� One sperm nucleus (1n) + one egg (1n) = zygote (2n)
� One sperm nucleus (1n) + two polar nuclei (1n each) = endosperm (3n)
� Elapsed time between pollination and fertilization� 24 – 48 hours
Pollen grain Three antipodal cells
Pollen tube
Two polar nuclei
Egg cell
Synergid cells
Tube-cell nucleus
Sperm nucleus
Fruit Structure
seed
exocarp
Ovule seed Ovary fruit
mesocarp
endocarp
pericarp
Categories of Fruits� Simple fruits: a single ovary produced by one flower
� Fleshy fruits (the entire pericarp and accessory parts are succulent)� Berry (bananas, grapes, papayas, tomatoes)� Pepo (cucumbers, melons, squashes)� Hesperidium (orange, lemon, lime, grapefruit)
� Dry-fleshy fruits (some parts of pericarp become dry while other parts remain succulent)
� Drupe (peaches, plums, cherries, apricots, olives, almonds)� Pome (apples, pear)
� Dry fruits (the entire pericarp is dry at maturity)� Dehiscent fruits (split to expose seeds at maturity)� Dehiscent fruits (split to expose seeds at maturity)
� Legume or pod (peas, beans)� Capsule (iris, poppy)� Silique (mustard)� Follicle (Delphinium)
� Indehiscent fruits (do not split at maturity)� Achene (sunflower)� Grain or caryopsis (corn, rice, wheat, barley)� Nut (walnut)� Schizocarp (carrots, parsley)� Samara (elm, maple)
� Aggregate fruits: many matured ovaries produced by a single flower which are all fused to a fleshy structure (strawberry, blackberry, raspberry)
� Multiple fruits: cluster of matured ovaries produced by separate flowers which are borne on a fleshy structure (pineapple, mulberries)
SenescenceSenescence
What is Senescence?
� Senescence is a “cellular transdifferentiation or metaplastic process in the course of which plastid structure and function are remodelled” - Thomas et al. (2003)
� Senescence refers to “a decline in age-specific � Senescence refers to “a decline in age-specific survival and reproduction with advancing age” [Roach (1993) Genetica 91: 53-64]
� In the physiological sense, it refers to
…“the orderly degenerative process leading to death of plant parts”
[Roach (1993) Genetica 91: 53-64]
Characteristics of Senescence
� the plasticity of senescenceincreasing plasticity
flowers < fruit < leaf
� Hallmarks of senescence:
Brief life span;
unidirectional
Some temporal
variation
Maximum temporal
variation; often
environmentally controlled
� Hallmarks of senescence:a. morphological changes: nuclear condensation, plasma
membrane blebbing, apoptotic bodiesb. physiological changes: remobilisation of nutrients (senescing
flowers ���� ovary or new flowers)c. molecular changes: degradation of DNA and lipids, activation
of genes related to programmed cell death
End of LectureEnd of Lecture